Generally, the widely-used peripheral input device of a computer system includes for example a mouse, a keyboard, a guiding trackball, or the like. For example, characters or symbols can be directly inputted into the computer system via the keyboard. As a consequence, most users and most manufacturers of input devices pay much attention to the development of keyboards.
Hereinafter, a key structure of a conventional keyboard will be illustrated with reference to FIG. 1. FIG. 1 is a schematic side cross-sectional view illustrating a conventional key structure. As shown in FIG. 1, the conventional key structure 1 comprises a keycap 11, a scissors-type connecting element 12, a rubbery elastomer 13, a membrane switch circuit member 14 and a base plate 15. The keycap 11, the scissors-type connecting element 12, the rubbery elastomer 13 and the membrane switch circuit member 14 are supported by the base plate 15. The scissors-type connecting element 12 is used for connecting the base plate 15 and the keycap 11. Consequently, the keycap 11 is movably fixed on the base plate 15.
The membrane switch circuit member 14 comprises plural key intersections (not shown). When one of the plural key intersections is triggered, a corresponding key signal is generated. The rubbery elastomer 13 is disposed on the membrane switch circuit member 14 and enclosed by the scissors-type connecting element 12. Each rubbery elastomer 13 is aligned with a corresponding key intersection. When the rubbery elastomer 13 is depressed, the rubbery elastomer 13 is subjected to deformation to push the corresponding key intersection of the membrane switch circuit member 14. Consequently, the corresponding key signal is generated.
The scissors-type connecting element 12 is arranged between the base plate 15 and the keycap 11, and the base plate 15 and the keycap 11 are connected with each other through the scissors-type connecting element 12. The scissors-type connecting element 12 comprises a first frame 121 and a second frame 122. A first end of the first frame 121 is connected with the keycap 11. A second end of the first frame 121 is connected with the base plate 15. Moreover, the first frame 121 comprises a first keycap post 1211 and a first base plate post 1212. The first frame 121 is connected with the keycap 11 through the first keycap post 1211. The first frame 121 is connected with the base plate 15 through the first base plate post 1212. The second frame 122 is combined with the first frame 121. A first end of the second frame 122 is connected with the base plate 15. A second end of the second frame 122 is connected with the keycap 11. Moreover, the second frame 122 comprises a second keycap post 1221 and a second base plate post 1222. The second frame 122 is connected with the keycap 11 through the second keycap post 1221. The second frame 122 is connected with the base plate 15 through the second base plate post 1222.
The operations of the conventional key structure 1 in response to the depressing action of the user will be illustrated as follows. Please refer to FIG. 1 again. When the keycap 11 is depressed, the keycap 11 is moved downwardly to push the scissors-type connecting element 12 in response to the depressing force. As the keycap 11 is moved downwardly relative to the base plate 15, the keycap 11 pushes the corresponding rubbery elastomer 13. At the same time, the rubbery elastomer 13 is subjected to deformation to push the membrane switch circuit member 14 and trigger the corresponding key intersection of the membrane switch circuit member 14. Consequently, the membrane switch circuit member 14 generates a corresponding key signal. When the keycap 11 is no longer depressed by the user, no external force is applied to the keycap 11 and the rubbery elastomer 13 is no longer pushed by the keycap 11. In response to the elasticity of the rubbery elastomer 13, the rubbery elastomer 13 is restored to its original shape to provide an upward elastic restoring force. Consequently, the keycap 11 is returned to its original position where it is not depressed. However, when the key structure 1 is depressed, the user cannot feel the depressing feedback.
With increasing development of science and technology, a mechanical key structure is introduced into the market. FIG. 2 is a schematic side cross-sectional view illustrating a conventional mechanical key structure. As shown in FIG. 2, the mechanical key structure 2 comprises a keycap (not shown), a pedestal 21, an upper cover 22, a push element 23, a linkage element 24, a first spring strip 25, a second spring strip 26 and a circuit board (not shown). The pedestal 21 is covered by the upper cover 22. The upper cover 22 has an opening 221. The linkage element 24 is located at a middle region of the pedestal 21. Moreover, the linkage element 24 is movable upwardly or downwardly relative to the pedestal 21. The first spring strip 25 is partially disposed within the pedestal 21, and located near a sidewall of the pedestal 21. The second spring strip 26 is partially disposed within the pedestal 21, and arranged between the linkage element 24 and the first spring strip 25. The push element 23 and the linkage element 24 are collaboratively disposed on the pedestal 21. The push element 23 is penetrated through the opening 221 and coupled with the keycap. Moreover, the first spring strip 25 and the second spring strip 26 are electrically connected with the circuit board.
Please refer to FIG. 2 again. The linkage element 24 has a protrusion structure 241. The protrusion structure 241 is extended from a sidewall of the linkage element 24 toward the first spring strip 25. Moreover, the first spring strip 25 comprises a fixing part 251 and an elastic part 252. The fixing part 251 is fixed on the pedestal 21. The elastic part 252 is extended from the fixing part 251. Moreover, the elastic part 252 is contacted with the protrusion structure 241 of the linkage element 24. Consequently, the elastic part 252 is movable relative to the fixing part 251.
When the keycap is depressed, the keycap is moved downwardly to push the push element 23. Consequently, the linkage element 24 connected with the push element 23 is moved downwardly. As the linkage element 24 is moved downwardly, the protrusion structure 241 of the linkage element 24 is contacted with the elastic part 252 and moved downwardly along the elastic part 252. While the linkage element 24 is quickly moved in response to the depressing force of the user, the linkage element 24 is quickly moved across the elastic part 252, and the elastic part 252 is pushed by the protrusion structure 241 of the linkage element 24. Consequently, the elastic part 252 is moved relative to the fixing part 251 to collide with the second spring strip 26. Since the first spring strip 25 and the second spring strip 26 are contacted with each other, the circuit board outputs a corresponding key signal. Moreover, while the first spring strip 25 and the second spring strip 26 are contacted with each other, a click sound is generated. Due to the click sound, the user can feel the depressing feedback.
Since the mechanical key structure 2 generates the click sound to provide the feedback feel while the keycap is depressed, the mechanical key structure 2 is favored by many users. However, the conventional mechanical key structure 2 still has some drawbacks. For example, since the conventional mechanical key structure 2 requires many components, the conventional mechanical key structure 2 is complicated and not cost-effective.
Therefore, there is a need of providing a key structure with low cost and capable of generating depressing feedback.